Field Of Electrochemistry Research Articles

Effects of Alkali Metal Ions on O2 and H2O2 Reduction Reactions at Pt Electrodes

In the field of electrochemistry, the oxygen reduction reaction (ORR) has been studied extensively for decades, largely because it is one of the most important electrochemical reactions in energy conversion systems such as fuel cells and metal-air batteries. The hydrogen peroxide reduction reaction (HPRR) has attracted attention recently because H2O2, which is a strong oxidizer, can be used as an oxidant in fuel cells, and also because H2O2 is involved in the ORR. It is generally accepted that the ORR proceeds either via a complete four-electron pathway or via a two-electron pathway. In acidic media, the four-electron ORR produces H2O as the final product (reaction 1), whereas the two-electron ORR produces H2O2 as an intermediate (reaction 2), which is further reduced to H2O (reaction 3). O2 + 4H+ + 4e- → 2 H2O (1) O2 + 2H+ + 2e- → H2O2 (2) H2O2 + 2H+ + 2e- → 2H2O (3) Pt has a good electrocatalytic activity toward the ORR and HPRR, and hence the reactions have been widely studied using Pt and Pt-based electrodes, including effects of electrolyte components and additives on the reactions. It has been reported that alkali metal ions, e.g., Li+, Na+, and K+, suppress the ORR and HPRR at Pt electrodes in alkaline electrolytes [1, 2]. The hydrated alkali metal ions and chemisorbed OH species on Pt non-covalently stabilize each other, leading to the formation of quasi-specifically adsorbed hydrated metal ion clusters, OHads-M+(H2O) x clusters, that blocks platinum active sites for electrochemical reactions. The suppression becomes stronger as the strength of the non-covalent interaction increases (K+ < Na+ < Li+). Consequently, the rest potential decreases in the order (Figure 1a). On the other hand, inorganic salts which are composed of the alkali metal ions, e.g., Na2SO4 and K2SO4, are often used as supporting electrolytes for electrochemical reactions. However, as we have reported before [3], the salts significantly affect the hydrogen evolution reaction (HER) in strongly acidic solutions. The rate of the HER decreased when the alkaline metal ions, i.e., Na+ and K+, are present in the solutions because the transport rate of H+ ions to the electrode surface decreased due to the ions. Thus, the HER current decreased as the concentration of the salts increased. We recently found that the HPRR at Pt electrodes in strongly acid solutions was suppressed by the salts. Although the rest potential was independent on the kind of alkali metal ions, the HPRR was suppressed due to the ions, as shown in Figure 1b. The suppression became stronger in the following order: Li+ < Na+ < K+, which is opposite to the order in the suppression due to the non-covalent interaction observed for alkaline media (see Figure 1a). In the presence of the alkaline metal ions, the decrease in the transport rate of H+ ions also caused an increase in the local pH at the electrode surface during the HPRR. When the concentration of H2O2 was higher than that of H+ ions, the local pH became strongly basic during the HPRR [4]. Note that the local pH remained acidic in the case of Figure 1b because of the lower concentration of H2O2. There arises the question: when the concentration of H2O2 is higher than that of H+ ions, does the local pH increase cause the non-covalent interaction? To answer the question, the effects of alkaline metal ions on the HPRR in strongly acid solutions are studied in this work. Furthermore, the ORR in the presence of the ions is also studied. REFERENCES [1] D. Strmcnik, K. Kodama, D. van der Vliet, J. Greeley, V. R. Stamenkovic and N. M. Marković, Nature Chemistry, 1, 466 (2009). [2] I. Katsounaros and K. J. J. Mayrhofer, Chem. Commun., 48, 6660-6662 (2012). [3] Y. Mukouyama, R. Nakazato, T. Shiono, S. Nakanishi and H. Okamoto, J. Electroanal. Chem., 713, 39 (2014). [4] Y. Mukouyama, H. Kawasaki, D. Hara, Y. Yamada, S. Nakanishi, J. Electrochem. Soc., 164 (2017) H675. FIGURE CAPTION Figure 1. The current (I) – potential (E) curves for a Pt-plate electrode in basic and acidic solutions measured under potential controlled conditions at a scan rate of 0.01 Vs-1. The basic solutions are 0.05 M alkali hydroxide (denoted as MOH) + 0.01 M H2O2, and the acidic ones are 0.05 M H2SO4 + 0.01 M H2O2 with or without 0.05 M alkali sulfate (denoted as M2SO4). Figure 1

Electrochemical Deposition of Tantalum from Ionic Liquids

Tantalum belongs to a class of metals called refractory metals (Niobium, Molybdenum, Tantalum, Tungsten and Rhenium) which are exceptionally resistant to heat and mechanical wear. Due to their tendency to form stable and dense oxide layers, these metals also possess a high resistance towards chemically agressive media. Therefore these metals can be used as protective coatings to build corrosion resistant parts, such as thermowells and valve bodies or for the production of special vacuum furnace components.[1] The electrochemical deposition of refractory metals is a cost-efficient method to coat materials of complex geometries. The negative reduction potential of Ta makes it impossible to use aqueous solutions. Thus ionic liquids (ILs), with an electrochemical window of 5 to 6 V, are promising alternative solvents and have been intensively used in different research fields of electrochemistry during the last years.[2] We have investigated the electrodeposition of Ta using different Ta halides (TaX5, X=F, Cl or Br) and different pyrrolidinium based ILs (1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [BMP][TFSI] and 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate, [BMP][OTf]). We could show that the combination of the precursor and the IL has a strong influence on the electrodeposition process of Ta. Furthermore using IR spectroscopy we found significant differences in the spectra of the different electrolytes which we correlated with results from computated spectra using Density Functional Theory (DFT). The aim of this combined IR/DFT approach is to identify the formed species in our electrolytes. We will present these data together with experimental results from investigations on the reduction mechanism using different electrochemical in-situ techniques (Differential Pulse Voltammetry, Rotating Ring Disk Electrode, Electrochemical Quartz Micro Balance) to show the influence of precursor-IL interaction on the electrodeposition process of Ta from ILs. Literature 1 F. Endres, A.P. Abbott, D. MacFarlane, Electrodeposition from Ionic Liquids, Wiley-VCH, Weinheim, 2008. 2 A. Ispas, B. Adolphi, A. Bund, F. Endres, Phys. Chem. Chem. Phys., 12 (2010) 1793-1803.

One-step synthesis of honeycomb-like Ni/Mn-PMo12 ultra-thin nanosheets for high-performance asymmetric supercapacitors

Polyoxometalates (POMs) are being increasingly applied in the field of electrochemistry owing to their excellent cluster-type open framework and ultra-high proton mobility. Honeycomb-like ultra-thin nanosheets of NiMn phosphomolybdate (Ni/Mn-PMo12) are successfully designed and synthesized on nickel foam via a one-step hydrothermal method. The Ni/Mn-PMo12 nanosheets at different ratios have similar morphology, with a three-dimensional structure consisting of ultrathin nanosheets that provides more electroactive sites and a shorter pathway for electron transfer and electrolyte diffusion. The optimized electrochemical performance of Ni/Mn-PMo12 is achieved using a Ni:Mn ratio of 2:1. The Ni/Mn-PMo12 nanosheets (Ni:Mn = 2:1) exhibit a high specific capacitance of 1950.5 F g−1 (975.3C g−1) at 1 A g−1, excellent property retention of 75.5% at 20 A g−1, and good cycle stability with 96.9% retention after 2000 cycles. The asymmetric supercapacitor assembled with Ni/Mn-PMo12 as the positive electrode and active carbon (AC) as the negative electrode shows a high energy density of 28.3 Wh kg−1 at a power density of 375 W kg−1, excellent rate performance, and good cycle performance (90.3% at a high current density of 2 A g−1 after 5000 cycles), suggesting that Ni/Mn-PMo12 nanosheets are highly promising for practical application in energy storage devices.

Highly Ordered Mesoporous NiCo2O4 as a High Performance Anode Material for Li-Ion Batteries.

The controlled synthesis of highly ordered mesoporous structure has attracted considerable attention in the field of electrochemistry because of its high specific surface area which can contribute the transportation of ions. Herein, a general nano-casting approach is proposed for synthesizing highly ordered mesoporous NiCo2O4 microspheres. The as-synthesized mesoporous NiCo2O4 microsphere materials with high Brunner-Emmett-Teller (BET) surface area (~97.77 m2g−1) and uniform pore size distribution around 4 nm exhibited a high initial discharge capacity of ~1,467 mAhg−1, a good rate capability as well as cycling stability. The superior electrochemical performance was mainly because of the highly porous nature of NiCo2O4, which rendered volume expansion during the process of cycling and shortened lithium-ions transport pathways. These properties showcase the inherent potential for use of highly ordered mesoporous NiCo2O4 microspheres as a potential anode material for lithium-ion batteries in the future.

The study on fuel-cell performance by using alkylimidazole ionic liquid as electrolytes for fuel cell

Ionic liquids are widely used in the field of electrochemistry because of its low melting point, wide electrochemical window and outstanding electrical conductivity. Ionic liquids are used as fuel-cell electrolytes in order to optimize the overall performance of fuel cells. Four ionic liquids have been investigated, such as 1-methylimidazolium hydrogensulfate [Hmim]HSO4, 1-n-butyl-3-methylimidazolium bromide [Bmim]Br, 1-n-butyl-3-methylimidazolium trifluoroacetate [Bmim]CF3COO, 1-n-butyl-3-methylimidazolium hydrogensulfate [Bmim] HSO4. At the same time, fuel cell shells made of PTFE and stainless steel were designed and processed. The anode and cathode electrode materials were prepared; then the above ionic liquids were used as the fuel-cell electrolyte in turn, The performance of the fuel cell was measured by voltammetry using hydrogen as a fuel and air as an oxygen source.

Silver Amalgam Nanoparticles and Microparticles: A Novel Plasmonic Platform for Spectroelectrochemistry

Plasmonic nanoparticles from unconventional materials can improve or even bring some novel functionalities into the disciplines inherently related to plasmonics such as photochemistry or (spectro)electrochemistry. They can, for example, catalyze various chemical reactions or act as nanoelectrodes and optical transducers in various applications. Silver amalgam is the perfect example of such an unconventional plasmonic material, albeit it is well-known in the field of electrochemistry for its wide cathodic potential window and strong adsorption affinity of biomolecules to its surface. In this study, we investigate in detail the optical properties of nanoparticles and microparticles made from silver amalgam and correlate their plasmonic resonances with their morphology. We use optical spectroscopy techniques on the ensemble level and electron energy loss spectroscopy on the single-particle level to demonstrate the extremely wide spectral range covered by the silver amalgam localized plasmonic resonances, ranging from ultraviolet all the way to the mid-infrared wavelengths. Our results establish silver amalgam as a suitable material for introduction of plasmonic functionalities into photochemical and spectroelectrochemical systems, where the plasmonic enhancement of electromagnetic fields and light emission processes could synergistically meet with the superior electrochemical characteristics of mercury.

Preparation of Graphene Materials and Their Applications in the Field of Electrochemistry

In the development of modern society, many new materials and technologies have been integrated into the development of various industries. As a new type of two-dimensional carbon nanomaterials, graphene has great advantages in physical and chemical properties and is widely used in various fields of development. Among them, the electrochemical method is one of the important ways to prepare graphene materials, which has the characteristics of quickness and environmental protection, and can effectively produce a large amount of high-quality graphene and its composite materials. Based on this, the paper introduces the preparation method of graphene materials and studies the application of graphene materials in the field of electrochemistry.

Electrocatalytic Activities of Gold Nanoparticles on Glassy Carbon Prepared By Simple Electrochemical Method

Nanoparticles (NPs) of noble metals such as gold and platinum are utilized in a wide range of applications in various fields because of their unique catalytic, electronic, and optical properties. Furthermore, NPs have large surface area to volume ratio, which leads to an increase in catalytic efficiency and also to a cost-reduction. A variety of methods using chemical reactions are currently available for synthesizing NPs in solution phase and also for controlling their shapes and properties. In the field of electrochemistry, platinum NPs (PtNPs) deposited on carbon materials such as graphite, glassy carbon, and carbon blacks have been extensively studied because they are useful as efficient electrocatalysts for fuel cells, water electrolysis, and so on. Nishimura et al. have developed a simple method for preparing shape-controlled PtNPs on a graphite surface [1]. In the method, the water electrolysis (2H2O → 2H2 + O2) was conducted at a constant current using the graphite electrode and a Pt electrode as the cathode and anode, respectively. The galvanostatic electrolysis was carried out for several hours in a strong acid solution such as HNO3 and H2SO4. During the electrolysis, the Pt anode slightly dissolved to form a small amount of Pt ions whereas the graphite cathode reduced the ions resulting in the formation of PtNPs. The method was cost friendly because PtNPs were obtained without any reducing and stabilizing agents, and also because 72 % of dissolved Pt ions were electrodeposited as PtNPs. In our previous report [2], we have shown that gold NPs (AuNPs) can be produced by galvanostatic electrolysis using an Au anode and a graphite cathode. This electrolysis was essentially the same as the simple method that has been used to prepare PtNPs [1]. The Au anode, where oxygen evolution occurred, dissolved to form Au ions (Au → Au3+ + 3e-) and the graphite cathode, where hydrogen evolution occurred, reduced them (Au3+ + 3e- → Au). We recently employed the galvanostatic electrolysis in order to prepare AuNPs on glassy carbon (GC). The experimental setup is shown in Figure 1a. AuNPs were uniformly deposited by conducting the electrolysis for two hours in 0.5 M H2SO4 solution, as can be seen in the SEM image (Figure 1b). Interestingly, the AuNPs showed a good electrocatalytic activity toward the reduction of nitrobenzene (C6H5NO2 + 6H+ + 6 e- → C6H5NH2 + 2H2O) compared with Au-wire electrode (Figures 1c and 1d). This is probably because AuNPs are enclosed by (111) planes, which will be discussed in the presentation. REFERENCES [1] T. Nishimura, T. Nakade, T. Morikawa, H. Inoue, Electrochimi. Acta, 129 (2014) 152. [2] Y. Mukouyama, Y. Fukuda, T. Nishimura, ECS Trans., 80 (2017) 1425. [3] Z. Chen, Z. Wang, D. Wu, L. Ma, J. Hazard Mater, 197 (2011) 424. FIGURE CAPTION Figure 1. (a) A schematic of the experimental setup for the simple galvanostatic electrolysis. Electrolysis solution: 0.5 M H2SO4. Cathode: GC disc. Anode: Au wire. (b) A SEM image of the GC cathode taken after conducting the electrolysis at 30℃ for two hours. Cathodic and anodic current densities were 10 and 2.5 mA cm-2, respectively. (c and d) Cyclic votammograms (CVs) measured in 0.1 M H2SO4 + 0.016 M nitrobenzene (NB) at a potential scan rate of 0.1 Vs-1. The working electrode used was (c) the AuNPs/GC electrode (total surface area of AuNPs: 0.16 cm2) and (d) an Au-wire electrode (surface area: 2.58 cm2). When the electrode potential (E) < ca. 0.2 V, NB was reduced to form aniline via a two-step reaction (see ref [3]): the formation of phenylhydroxylamine (C6H5NO2 + 4H+ + 4e- → C6H5NHOH + H2O) and its consecutive reduction to aniline (C6H5NHOH + 2H+ + 2e- → C6H5NH2 + H2O). Figure 1

The capacitance and electron transfer of 3D-printed graphene electrodes are dramatically influenced by the type of solvent used for pre-treatment

3D-printing (or additive manufacturing) is presently an emerging technology that promises to reshape traditional manufacturing processes. The electrochemistry field can certainly take advantage of this fabrication tool for sensing and energy-related applications. Polymer/graphene filaments commonly used for the fabrication of 3D-printed electrodes show poor electrochemistry in the native state, requiring post-fabrication activation procedures. In the present work, solvent activation of graphene/polymer-based 3D-printed electrodes was investigated, using both polar aprotic solvents (DMF and acetone) and polar protic solvents (EtOH, MeOH, and H2O). Differences were noted with respect to the weight loss and surface morphologies of the activated electrodes prior to their use, depending the solvent used. The electrodes activated in polar aprotic solvents exhibit a dramatic increase in heterogeneous electron transfer rate using the Fe(CN6)4−/3− redox couple. Moreover, the activation medium has a crucial influence on the electrochemical double layer. We wish to provide meaningful insight to researchers by comparing results obtained with 3D-printed electrodes fabricated from graphene/polymer filaments and drawing attention to the influence of the solvents used in their activation.

Impressive Proton Conductivities of Two Highly Stable Metal-Organic Frameworks Constructed by Substituted Imidazoledicarboxylates.

There is great interest in the promising applications of proton-conductive metal-organic frameworks (MOFs) in the field of electrochemistry. Thus, seeking more types of MOFs with high proton conductivity is of great importance. Herein, we designed and prepared two substituted imidazoledicarboxylate-based MOFs, {[Cd( p-TIPhH2IDC)2]·H2O} n [1; p-TIPhH3IDC = 2- p-(1 H-1,2,4-triazolyl)phenyl-1 H-4,5-imidazoledicarboxylic acid] and [Sr(DMPhH2IDC)2] n [2; DMPhH3IDC = 2-(3,4-dimethylphenyl)-1 H-imidazole-4,5-dicarboxylic acid], and fully explored their water-assisted proton conduction. The best conductivity for 1 of 1.24 × 10-4 S·cm-1 is higher than that of most previous conductive Cd-MOFs under similar conditions. 2 has the highest conductivity (0.92 × 10-3 S·cm-1) among the reported conductive Sr-MOFs. Via structural analysis, Ea values, water vapor adsorptions, and powder X-ray diffraction and scanning electron microscopy tests, reasonable proton pathways and conduction mechanisms were highlighted. It should be emphasized that the N-heterocyclic units (imidazole and triazole) and carboxyl and hydrogen-bonding networks in the frameworks all play crucial roles in the transmission of proton conductivity. Our research offers more choice for the preparation of desired proton-conductive materials.

Immobilizing Pd nanoclusters into electronically conductive metal-organic frameworks as bi-functional electrocatalysts for hydrogen evolution and oxygen reduction reactions

Although noble metals, especially Pt and Pt-based materials, are the most efficient catalysts for electrocatalysis, their high cost, low abundance and the strong tendency to aggregate of nanoparticles hinder their further commercial applications. In recent years, metal-organic frameworks (MOFs) have been found to be promising templates for immobilizing nanoclusters (NCs) as advanced catalysts. However, their poor electrical conductivities largely limit their applications in the field of electrochemistry and electrocatalysis. In this study, electrically conductive MOF-74 is chose as template to immobilize tiny Pd NCs in the pores (Pd@MOF-74). Unlike the usually reported MOF-based electrocatalysts, without the post calcination process, the Pd@MOF-74 exhibited excellent electrocatalytic performances for both hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). Moreover, due to the tiny size and the high dispersion of Pd clusters confined in the MOFs, the loading of noble Pd metal can be largely reduced for the catalysis. Meanwhile, the Pd clusters immobilized in the MOF-74 showed higher long-term durability in both acid and alkaline electrolytes than commercial Pt/C.

Origin of the Electrochemical Stability of Aqueous Concentrated Electrolyte Solutions

The electrochemical stability of an electrolyte solution, its so-called "potential window", is simply determined by the oxidative potential and reductive potential of the solvent, if solutes dissolved in the electrolyte solution are electrochemically stable within the potential window of the solvent. Water is the most conventional solvent in the field of electrochemistry, and its potential window is as narrow as 1.23 V, thermodynamically. Practically, however, the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) need certain overpotentials, which extends the potential windows of aqueous solutions. Besides the catalytic activities of the electrode materials, the properties of aqueous solutions such as hydration structures and salt concentrations also affect the potential window.Recently, aqueous rechargeable lithium batteries (ARLBs) have attracted much attention due to their low cost and safety. However, the working voltage of ARLBs is limited to below 1.5 V due to the narrow potential window of water. Recently, a few papers have discussed the potential window of concentrated aqueous solutions with neutral pH. However, there are still fundamental unanswered questions regarding the pH-dependence of the potential window of water. In this study, the potential window of concentrated electrolyte solutions with neutral pH and the expansion of the potential window were investigated from the viewpoint of the local pH change and water concentration. Here, we shed light on the dependence of the potential window of water on local pH changes and water concentrations. Next, we focused on the water concentration, since the potential windows are determined by the water electrolysis reactions (OER and HER). The potential windows are shown in Fig. 1 as a function of the water concentrations. In this study, the onset potential of the OER/HER was defined when the current density was ± 0.1 mA cm-2 in CVs at 1 mV s-1. There are two clear tendencies in Fig. 1. First, the windows in neutral pH electrolyte solutions (closed symbols in Fig. 1) were obviously wider than those in acidic/alkaline electrolyte solutions (open symbols in Fig. 1), even at a dilute salt concentration (ca. 55 M water concentration). Second, the windows in neutral pH electrolyte solution (closed symbols in Fig. 1) were not affected by the kind of the electrolyte salt, but depended linearly on the water concentration. The windows were expanded when the water concentration decreased, i.e., the electrolyte salt concentrations increased. Potential windows of aqueous solutions were investigated systematically using various salts at different concentrations. Cyclic voltammetry measurements of Pt electrodes revealed two important points. First, the potential window in unbuffered neutral pH solution was broader than that in acidic/alkaline solutions. This expansion of potential windows can be explained by the shift in the reaction potential with local pH changes in the vicinity of the electrode. Second, the potential windows were not affected by electrolyte salts, but rather depended linearly on the water concentration. The difference for OER overpotentials was much larger than that for HER overpotentials. While HER overpotentials were derived from a local pH change, OER overpotentials were derived from both a reduced water concentration and local pH change. This study highlights the importance of these two main factors (water concentration and local pH change) in determining the potential windows of concentrated electrolyte solutions. Figure 1

Review—Biosensing and Biomedical Applications of Graphene: A Review of Current Progress and Future Prospect

Graphene has generated widely interest in biosensor study because it had a large surface area, excellent electrical and thermal conductivity, high mechanical strength and other unique physical and chemical properties. In this paper, graphene was reviewed from three aspects. Firstly, several common fabrication methods and characteristics of graphene were introduced. Secondly, applications of the nanosized graphene (NG) and nanosized graphene oxide (NGO) in biosensor and medical imaging were discussed. The NG and NGO had the characteristics of photoluminescence. Based on the fluorescence quenching nature of the graphene surface, the targeting molecules could be confirmed by detecting the fluorescent substance. In addition, the graphene oxide (GO) had a promising prospect in the field of surface-enhanced Raman imaging. In the field of electrochemistry, graphene and its derivatives could be modified on the surface to couple with ligands and antigens and were able to detect specific biomolecules, such as glucose, DNA, proteins and etc. Thirdly, this paper introduced graphene applications in medical treatment. Due to the inherent high near-infrared (NIR) absorbance, graphene materials were widely used in the treatment of in vivo cancer photothermal therapy. The combination of the graphene, anticancer drugs, and specific antigens was highly efficient for drug delivery. This paper summarized the achievements of graphene materials in the medical diagnostics, the presents challenges, and the future prospect.

Electrochemically Recognizing Tryptophan Enantiomers based on Carbon Black/Poly-l-Cysteine Modified Electrode

Construction of efficient and convenient sensors for recognition of chiral enantiomers is of much significance in the field of electrochemistry and life sciences. Herein, we designed an effective chiral interface for the successful identification of tryptophan (Trp) enantiomers by electrodepositing l-cysteine on the surface of glass carbon electrode modified with carbon black. The structure and morphology of the prepared sensor was characterized by scanning electron microscopy (SEM) and electrochemical methods. Compared with l-tryptophan (L-Trp), the sensor exhibits favorable chiral recognition towards D-tryptophan (D-Trp) with a separation coefficient of 2.50. Compared with existing studies on electrochemical chiral recognition of Trp enantiomers, our designed chiral platform boasts of a wider linear range (1.0–1400.0 μM) and lower limits of detection thus, 0.33 μM and 0.45 μM for L-Trp and D-Trp respectively. In addition, the proposed sensor has the capacity to recognize chiral molecules in Trp isomers mixture and the potential for the identification of other amino acids.

Gel Polymer Electrolytes Modified Nanoparticles or Copolymers and Polymerized in Magnetic and Electric Fields

Gel polymer electrolytes are perspective electrolytes for new types of Li-ion batteries today. The properties respectively advantages of these gels can be used also in other fields of electrochemistry. The gel polymer electrolyte is composed of a conductive component (liquid electrolyte) and the polymer component (methacrylate-based polymer). In this paper, I present fundamental characteristics of gel polymer electrolytes modified nanoparticles or copolymers and preparation of these gel polymer materials with nanoparticles or copolymers polymerized in electric and magnetic fields.

Ti3C2Tx MXene/polyaniline (PANI) sandwich intercalation structure composites constructed for microwave absorption

MXene, as a new 2-dimensional (2D) material, has excellently potential applications in the field of electrochemistry owing to its high conductivity and fast charge transporting speed. Especially, MXene/polymer composites have attracted widely attentions due to their extensive application in the area of multi-functional materials. Herein, the composites of Ti3C2Tx MXene/polyaniline (PANI) with different PANI contents have been successfully prepared. The microwave absorption mechanism of these materials was investigated. Attributing to the multiple layer structure, the dielectric property of Ti3C2Tx MXene and PANI, and the synergistic effect between the Ti3C2Tx and PANI, the as-prepared composites possessed a specific microwave absorbing behavior. With a proper content of PANI, the MXene/PANI composites in a paraffin matrix exhibited a maximum reflection loss of −56.30 dB at 13.80 GHz with the thickness of 1.8 mm. In addition, the effective absorption bandwidth (>90%) ranged from X-band (8–12.4 GHz) to Ku-band (12.4–18 GHz) with the tunable thickness ranging from 1.5 to 2.6 mm. The results indicate that MXene/PANI composites has great potential to be used in the field of microwave absorption.

Effect of the external electric field on the electronic structure, spectroscopic features, NLO properties, and interionic interactions in ionic liquids: A DFT approach

Ionic liquid (IL)s are a unique group of chemicals with extraordinary physical and chemical properties. Due to the advantage of the tunability of their features by varying the ion compositions and either IL/IL or IL/conventional solvent mixing ratios, uncountable functions of them have been discovered. In the field of electrochemistry and energy applications, the function of ILs under external field should also be understood well. The most fundamental way of gaining insight into the function of a substance is to study the structure. Therefore, this work focuses on the investigation of structural variations of an exemplary IL, 1-hexyl 3-methylimidazolium chloride (HmimCl), under external electric field (EEF) via ab initio quantum chemistry calculations.Field dependent geometry analysis show that the interionic bond and the molecular conformation can be modulated by the strength and the direction of the applied field, and the disassociation occurs at ~0.7 V/Å level. Mulliken, atomic polar tensor, and natural bond orbital charges were obtained within field dependency and their correlation was examined. Charge displacement curves were constructed to visualize the field inducement on the charge transfer. Interionic interactions were profiled as hydrogen, van der Walls, and steric effect by using reduced density gradient analysis and the breaking of the single hydrogen bond was determined to occur at ~0.6 V/Å level. The vibrational spectra (IR and Raman) were simulated and the critical peaks that are affected by the field inducement were interpreted. The analysis of the field dependent Nonlinear Optical (NLO) properties shows that the only important component is in the field direction for the field intensity >0.2 V/Å. Electronic transition properties determined via TD-DFT calculations with B3LYP/6-311G** level of theory indicate that the UV–Vis spectrum and underlying transitions are depended on the direction of the field, and experience a bathochromic shift with increasing inducement showing that the IL becomes more susceptible to excitation.

Kinetics and Mechanism of Silver Dissolution in Aqueous Sodium Nitrate

The kinetics of the electrochemical oxidation–reduction of silver in aqueous solutions of sodium nitrate was studied by potentiometry. The effect of the electrolyte concentration and temperature and sweep rate on the electrochemical behavior of silver was studied. To characterize the mechanism of silver electrooxidation, the following kinetic parameters were calculated: ion transport number (αn), diffusion coefficient (D), heterogeneous rate constant of the electrode process (Ks), and effective activation energy of the process (Eef). The data obtained may be of interest to specialists in the field of electrochemistry.

Assessment of commercial feasibility of the device for the combined cutting of conducting materials by calculation of integrated koefficient

Authors have considered the problem points connected with commercialization of university intellectual property items in the field of electrochemistry, namely the device of electrochemical cutting of conducting materials. Key criteria for evaluation of an intellectual property item are designated. The method of calculation of commercial appeal which is most acceptable for this development on the basis of the generalized integrated coefficient, theoretically is offered and its commercial value is almost proved.

Substrate-mediated and temperature-modulated long-range interactions between bromine adatom stripes on Cu(1 1 1)

Understanding long-range adsorbate-adsorbate interactions on surfaces, such as halogens on metal surfaces, is important in the fields of electrochemistry, catalysis, and thin film growth. In this work, we computationally studied bromine (Br) stripe formations on Cu(1 1 1). These stripes are found to be surface-mediated and temperature-modulated; they are facilitated by BrCu bonding guided by self-patterning of Cu(1 1 1) surface frontier orbitals and by strain release induced stripe migration in a thermal bath. The calculated surface wave-functions in frontier occupied states show stripe-like electron distributions and thus the favorable sites of Br adsorption on Cu(1 1 1) are also stripe-like. The temperature effect is notable in that the thermal energy of 50 K easily dominates Br stripe gathering in (√3×√3)R30° structures. Corresponding electron stripes on the surface could be generated, widened, shrunk or removed depending on spacing changes of Br stripes, thus reflecting diverse and changeable formation features for dynamic patterns of adsorbates on Cu(1 1 1).